What were the main causes of World War I? Learn about how mutual defense alliances, imperialism, militarism, and nationalism all played a part.

World War I began in 1914, after the assassination of Archduke Franz Ferdinand, and lasted until 1918. During the conflict, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire (the Central Powers) fought against Great Britain, France, Russia, Italy, Romania, Japan and the United States (the Allied Powers). World War I saw unprecedented levels of carnage and destruction due to new military technologies and the horrors of trench warfare.

No Man's Land

When Europe plunged into war in 1914, Wilson saw America's role as that of peace broker.

“Freedom of the seas” was the early 20^th century idea that the world’s oceans served as a global commons for carrying cargo and facilitating commerce. As both a communal property and throughway, the seas thus could not be controlled by any belligerent power outside of territorial waters, according to freedom of the seas.

How was propaganda used to change people's views in World War One? Find out in this Bitesize Primary History guide.

How George Creel sold the Great War to America, and America to the world.  

3,000 women gathered in Washington to create the Women's Peace Party & promote pacifism. As the US readied to enter WWI, many saw them as unpatriotic.

World War I Following nearly three years of intense combat since the onset of World War I, America’s allies in Europe were facing starvation. Farms had either

Like the other warring nations, the United States had to organize its industries in support of its military effort. The War Industries Board was designed to provide the necessary coordination and control. Despite a halting start, it made significant progress toward meeting its objectives, especially in 1918.

Reparations, a levy on a defeated country forcing it to pay some of the war costs of the winners. The most prominent example is the reparations levied on Germany after World War I to compensate the Allies for some of their war costs. Learn more about reparations and their use in this article.

Though Wilson championed the League of Nations, the United States would never join.

Journey through the story of the Great War with our Interactive WWI Timeline, covering the world events of 1914 - 1920.